Comment 7 for bug 1882205

Also seen in another hook (leader-elected) while deploying the charm-nova-cloud-controller focal-victoria zaza test bundle:

https://review.opendev.org/#/c/748650/
https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline_func_full/openstack/charm-nova-cloud-controller/748650/1/6786/index.html

2020-09-07 15:02:50 ERROR juju-log Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/charms/reactive/__init__.py", line 74, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 390, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 359, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 181, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/charm/reactive/mysql_innodb_cluster_handlers.py", line 279, in db_router_respond
    if instance.create_databases_and_users(db_router):
  File "lib/charm/openstack/mysql_innodb_cluster.py", line 1114, in create_databases_and_users
    password = self.configure_db_router(
  File "lib/charm/openstack/mysql_innodb_cluster.py", line 1228, in configure_db_router
    password = rw_helper.configure_router(host, username)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/charmhelpers/contrib/database/mysql.py", line 757, in configure_router
    self.create_router_grant(username, remote_ip, password)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/charmhelpers/contrib/database/mysql.py", line 730, in create_router_grant
    cursor.execute("GRANT CREATE USER ON *.* TO '{}'@'{}' WITH GRANT "
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/MySQLdb/cursors.py", line 206, in execute
    res = self._query(query)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/MySQLdb/cursors.py", line 319, in _query
    db.query(q)
  File "/var/lib/juju/agents/unit-mysql-innodb-cluster-1/.venv/lib/python3.8/site-packages/MySQLdb/connections.py", line 259, in query
    _mysql.connection.query(self, query)
MySQLdb._exceptions.OperationalError: (1290, 'The MySQL server is running with the --super-read-only option so it cannot execute this statement')